1. Field of the Invention
The present invention relates to an unwrapping apparatus for unwrapping a stretch-wrapped load comprised of a pallet, a plurality of articles palletized on the pallet and a stretchable film wrapping the articles and the pallet together, and in particular, the present invention relates to an unwrapping apparatus for unwrapping a stretch-wrapped load by cutting a stretchable film of the stretch-wrapped load and removing it so as not to allow the film of any shrinkage until it (or the film) completely separates from the palletized articles.
2. Description of the Related Art
In transportation, one known form of load is a "pallet-wrapping" or "unitizing", in which articles are placed on a pallet and the articles are bound together with the pallet by means of, for example, a strapping, a shrink wrapping or a stretch wrapping. The stretch wrapping involves the use of a stretchable or elastic plastic film that is automatically wound around the articles and the pallet under tension to unitize the articles and the pallet together. A so-called "pallet stretch wrapping" can be performed with less labor and has become one of the most popular pallet-wrapping techniques. In an example of such palletized and stretch-wrapped load, glass bottles, PET (polyethylene terephthalate) bottles, or metallic cans are placed on a pallet via separate sheets or tier sheets and they are stretch-wrapped together with a stretchable film. Such a palletized and stretch-wrapped load may be transported to a user.
Proposals have been made on an apparatus and a method for stretch wrapping and disclosed in, for example, Japanese Examined Patent Publication (Kokoku) No. 58-7524, No. 59-9403, No. 59-40682, No. 59-46845, No. 59-52087, and No. 61-27254.
In this manner, automated systems have been developed regarding the stretch wrapping. However, unwrapping the stretch-wrapped load has not yet been fully developed and in many cases, unwrapping is carried out manually by cutting the stretchable film encircling the load by a hand cutter, removing the stretchable film from the load, and crumpling it to discard same.
Proposals have been made for an automatic unwrapping apparatus and disclosed in, for example, Japanese Unexamined Patent Publication (Kokai) No. 48-58995, No. 49-95788, No. 1-111642, and No. 2-166033. These machines automatically remove the stretchable film from the stretch-wrapped load, but they must have a complex structure and working steps to completely remove the stretchable film from the palletized and stretch-wrapped load.
For example, in Japanese Unexamined Patent Publication (Kokai) No. 48-58995, the unwrapping apparatus includes four movable grippers 5 arranged at four corners of the palletized and stretch-wrapped load to be unwrapped, a pair of cutters 7 arranged at opposite side surfaces of the load, floating rollers 8 arranged at the remaining opposite side surfaces of the load to cooperate with the grippers 5, a further top cutter 11, and a retractable support 12 for the floating rollers 8. The unwrapping apparatus further includes supporting and actuating arrangements to move these elements in many directions.
In Japanese Unexamined Patent Publication (Kokai) No. 49-95788, the unwrapping apparatus includes a conveyor 4 having an elevator 6, cutter unit 19 having vertical chains 16 and cutters 17 attached to the chains 16 to cut the opposite side of the cover (of stretchable or shrinkable film) 3, winding rollers 30 arranged at four corners of the elevator 6 for nipping the cut cover 3, suction heads 31 arranged at four sides of the elevator 6 for supporting the four sides of the cover 3, a top cutter 34, and a top trolley 44 with top suction heads 46. The top of the cover 3 is cut first and then the remaining portion is cut into four side pieces. Each of these four side pieces is held at its lower portion by the suction head 31 and the upper portion of the cut side piece falls and is nipped by the winding rollers 30.
In Japanese Unexamined Patent Publication (Kokai) No. 1-111642, the unwrapping apparatus includes a pre-cutting device arranged at the station A and comprising bottom corner cutter units 13 to cut the cover of stretchable or shrinkable film bottom corners of the palletized load along cutting lines 18 (FIG. 3), suction heads 19 to cooperate with the bottom corner cutter units 13, side cutter units 14 to cut slits 21 (FIG. 1). The unwrapping apparatus also includes, at the station B, a lifter conveyor 26, suction heads 27, heat cutters 40 adjacent the suction heads 27, lateral spreading units 33 having fingers 36, and elevated frames 38 having main cutter units 41 with hot air nozzles 44. The main unwrapping sequences are shown in FIGS. 7 to 10.
In Japanese Unexamined Patent Publication (Kokai) No. 2-166033, the unwrapping apparatus includes a cutter unit C with a hot air cutter 25, a holding unit H having a suction head 33, and a removing unit R having a pair of pinch rollers 41 and 42. The holding unit H can hold the film 2 while the cutter unit C cuts the film 2. The holding unit H can also act to guide the cut sheet 2 to the removing unit R.
In the stretch wrapping, the stretchable film in tension unitizes the articles and the pallet together and maintains contact with the articles located at the peripheral regions of the stretch-wrapped load. The stretched film may enter any gaps or cavities between the peripheral edges of the separate sheets or between the peripheral edges of the separate sheet and the pallet, especially at the corners of the stretch-wrapped load due to the unitizing force of the stretched film, so the film contacts the articles in the stretch-wrapped load. When the stretch-wrapped load is to be unwrapped, the stretchable film is cut, causing the stretchable film to suddenly shrink due to an immediate release from the tension applied to it. This sudden (or rapid) shrinkage of the stretchable film is liable to cause the stretchable film to move or shift the palletized articles in contact with said film on the separate sheet, and if the articles are empty and light, they may fall down out of the separate sheet, in particular from the uppermost separate sheet. Also, a similar problem arises when the already cut stretchable film is separated (or removed) from the palletized articles.
The unwrapping apparatuses described in the above Patent Publications do not have appropriate means to solve this problem and are not adapted for unwrapping the stretch-wrapped load in which empty and light articles, such as bottles are placed in bulk therein.
Also, the stretchable film must be disposed (to waste) after it is cut and removed from the palletized articles. But the unwrapping apparatuses described in the above Patent Publications do not have appropriate means to easily dispose the used and bulky stretchable film (to waste).